The present invention relates generally to x-ray tubes and, more particularly, to a high emissive coating on a target shaft of an x-ray tube.
X-ray systems typically include an x-ray tube, a detector, and a bearing assembly to support the x-ray tube and the detector. In operation, an imaging table, on which an object is positioned, is located between the x-ray tube and the detector. The x-ray tube typically emits radiation, such as x-rays, toward the object. The radiation typically passes through the object on the imaging table and impinges on the detector. As radiation passes through the object, internal structures of the object cause spatial variances in the radiation received at the detector. The detector then emits data received, and the system translates the radiation variances into an image, which may be used to evaluate the internal structure of the object. One skilled in the art will recognize that the object may include, but is not limited to, a patient in a medical imaging procedure and an inanimate object as in, for instance, a package in a computed tomography (CT) package scanner.
X-ray tubes include a rotating anode structure for the purpose of distributing the heat generated at a focal spot. The anode is typically rotated by an induction motor having a cylindrical rotor built into a cantilevered axle that supports a disc-shaped anode target and an iron stator structure with copper windings that surrounds an elongated neck of the x-ray tube. The rotor of the rotating anode assembly is driven by the stator. An x-ray tube cathode provides a focused electron beam that is accelerated across a cathode-to-anode vacuum gap and produces x-rays upon impact with the anode. Because of the high temperatures generated when the electron beam strikes the target, it is necessary to rotate the anode assembly at high rotational speed.
Newer generation x-ray tubes have increasing demands for providing higher peak power, thus higher average power as well. Higher peak power, though, results in higher peak temperatures occurring in the target assembly, particularly at the target “track,” or the point of impact on the target. Thus, for increased peak power applied, there are life and reliability issues with respect to the target. Such effects may be countered to an extent by, for instance, spinning the target faster. However, doing so has implications to reliability and performance of other components within the x-ray tube such as the target and the bearing assembly. And, although spinning the target faster may reduce the peak focal track temperature, there is limited enhancement or improvement in the overall average power capability of the x-ray tube. As such, spinning faster has minimal impact on decreasing the operating temperature of the bearing assembly for a given average power.
Therefore, it would be desirable to have a method and apparatus to improve thermal performance and reliability of an x-ray tube target and bearing.